After Effects Error Asked To Create Unknown Property Of Type Fix [updated] | High-Quality & Recommended

: /Applications/Adobe After Effects (version)/Scripts/ScriptUI Panels

If you’ve been working in Adobe After Effects long enough, you’ve probably seen a few head-scratching error codes. But the one that has been popping up more frequently lately—especially for users working with expressions, templates, or specific third-party scripts—is:

The most frequent cause is trying to open a project file in an older version of After Effects than the one it was saved in. While After Effects is generally backwards compatible, it is not always forwards compatible. The Solution Ensure your Creative Cloud app is fully updated. The Solution Ensure your Creative Cloud app is fully updated

This typically happens in one of three scenarios:

This error usually pops up when After Effects is trying to interpret a script, expression, or pseudo-effect (a custom controller) that it does not recognize or that has become corrupted. As of 2026, this often relates to bridging older project files with the latest, highly optimized AE expression engine. This error usually happens when After Effects tries

This error usually happens when After Effects tries to load a project, preset, or script that references a "Pseudo Effect" or a specific property type that isn't installed on your system . 🛠️ Core Fixes

or scripts running in the background can trigger this error during startup. Corrupt Preferences highly optimized AE expression engine.

: Templates created in older versions of AE may use code that is no longer supported by the modern JavaScript engine. File > Scripts > Update Legacy Expressions.jsx

Install the required third-party software (e.g., Trapcode, Element 3D, or Sapphire).